1. Field of the Invention
The present invention relates to arthroplasty, i.e., an operation to restore motion between the bones of a skeletal joint, and concomitant function to muscles, ligaments and other tissue which control that joint. The present invention more particularly relates to cementing prostheses to bone.
2. The Prior Art
A prosthesis for a freely movable (synovial) skeletal joint comprises at least one member that has a configuration which presents an articulating surface and an anchor surface. The anchor surface is anchored to bone. The articulating surface bears against the corresponding articulating surface of another member.
In conventional hip, knee and like arthroplasties, for example, a member of a plastic or metal prosthesis is positioned with an anchor surface that is directly in contact with and mechanically anchored to bone either with or without cement. In the absence of cement, the integrity of the anchor typically relies upon the configuration of the anchor surface of the prosthesis member and intergrowth of bone and/or tissue with that surface. In the presence of cement, the integrity of the anchor typically relies, not only on adhesion, but also upon mechanical interlocking between (1) the cured cement, and (2) the adjoining or conjunctive anchor surfaces of the prosthesis member and the bone. Various problems have been encountered in implementing the above techniques.
Metal prostheses conventionally have been composed of either a titanium alloy or a cobalt-chromium alloy. Although these materials have advantages. in strength and surface integrity, they may suffer from problems that include less than desired in vivo performance. Plastic prostheses conventionally have been composed of ultra high molecular weight polyethylene (UHMWPE), and the cement therefor conventionally has been composed of polymethyl methacrylate (PMMA). These materials have excellent biocompatibility, but have suffered from poor adhesion to each other, as a result of which loosening occurs and debris is produced.